We just discoved that a vent pipe in our attic somehow froze and shattered. It was full of ice. We are confused about how all the water came to sit in the pipe. The pipe runs horizontal for about 25 feet until it reaches the upward pipe that goes out the roof. This pipe that broke only vents the kitchen sink and dishwasher. My husband said that the pipe is pitched back toward the kitchen down pipe but I finally climbed up there myself and I cannot confirm that because the pitch is so gradual I couldn't see it for sure. My question is: How does so much water accumulate when it is only condensation venting up the pipe? How can we prevent this from happening again? Would it be possible to just cut this pipe and put a staight pipe venting the sink and dishwasher into the attic?

Perhaps some leaves or other crud got into the vent pipe through the open end in the roof, causing a blockage somewhere down the line; then, over time, rainwater filled in the space between the blockage and the roof.

A blockage like that would have gone pretty much unnoticed until now, since it wasn't blocking any fixtures from draining properly; it's only a vent line.

Try snaking (whatever's left of) the vent pipe and see if you come up with anything (or maybe just pour some drain cleaner down it).

Moishe

You don't want to vent a drain into the attic. The toxic sewer gases could leak down into the house. The moisture in the attic would be bad too. I am sure Tom will say it violates code.

Make sure what is left is clear. If water disappears when you pour it in, that is good enough. Then either go straight up through the roof, or repair the line making sure it is pitched for incoming rain to go down the drain.